1. Technical Field
The present invention relates to a projector, a projection system, an image display method, and an image display program each for sliding pixels of a plurality of image light beams from each other, thereby displaying a high-resolution image.
2. Related Art
In the past, there have been known image processing devices for performing a sharpening process for emphasizing a contour portion of an image in order for preventing blur and so on causing degradation in image quality (see, e.g., JP-A-9-91419 (Document 1) and JP-A-2002-83294 (Document 2)).
The image processing device described in the Document 1 detects an unclear portion in the image data of the input image. Then, the image processing device executes the sharpening process using a so-called Laplacian filter of calculating quadratic differentials of the pixel value of each of the pixels of the detected portion with respect to an x-direction and a y-direction, and adding them to each other.
The image processing device described in the Document 2 executes a so-called unsharpness mask process of calculating a high-frequency component, the difference between the input image and a smoothed image, and then adding the result of multiplication of the high-frequency component by a certain gain to the input image.
Incidentally, there is known a so-called oblique pixel slide method of using a plurality of image projection devices such as a plurality of optical engines or a plurality of projectors, and sliding the pixels of the image light beams emitted from the respective image projection devices a half pixel in an oblique direction, thereby displaying an image with a higher resolution.
However, since the plurality of optical engines mounted on such a projector and the plurality of projectors constituting such a projection system each have an individual difference, and have the sharpness different from each other, there is caused a problem that it is not achievable to display a normal image by the sharpening.
Here, the problem described above will be explained in detail using an example shown in FIGS. 9A, 9B, 10A, and 10B.
FIGS. 9A and 9B are diagrams showing luminance values at a predetermined pixel position in the case in which the same image signal is input to optical engines (PJ1, PJ2) having optical transfer functions (specifically, modulation transfer functions (MTF)) different from each other. FIGS. 10A and 10B are diagrams showing the luminance values at the predetermined pixel position in the case in which the image light beams from the optical engines PJ1, PJ2 are displayed using the oblique pixel slide method in FIGS. 9A and 9B. Further, “x” shown in FIGS. 9A, 9B, 10A, and 10B denotes the coordinate position in the display image with respect to the horizontal direction, and “y” denotes the coordinate position in the display image in the vertical direction.
As shown in FIG. 9A, when the same image signal is input to the optical engines (PJ1, PJ2) with the MTF different from each other, the luminance values vary along change curves corresponding to the respective MTF in the vicinity of the edge (x=a). When the same sharpening process is executed on such an image signal, the execution of the sharpening process results in the states different from each other as shown in FIG. 9B. Further, in the case in which the image light beams output from these optical engines PJ1, PJ2 are displayed using the oblique pixel slide method, a variation in the luminance value is caused in the vicinity of the edge portion as shown in FIGS. 10A and 10B. Here, the broken lines show the ideal luminance values in the case in which the image light beam having the same sharpness are projected from the optical engines PJ1, PJ2. As shown in FIGS. 10A and 10B, since the sharpness is emphasized in each of the optical engines PJ1, PJ2 when the sharpening process is executed thereon, the luminance difference becomes larger compared to the case in which the sharpening process has not been executed. Therefore, in the oblique pixel slide method, there is a problem that if the sharpening process is executed directly on the image signal input to the optical engines PJ1, PJ2, the luminance difference in the edge portion becomes larger, and a noise such as jaggy becomes noticeable.